HFCs REMAIN UNDER 0.8 % OF THE ATMOSPHERIC LEVEL OF ALL GREENHOUSE GASES

The US NOAA (National Oceanic and Atmospheric Administration) has released its 2014 update of the AGGI (Annual Greenhouse Gas Index), intended to follow the evolution of the radiative forcing (ability of all greenhouse gases to trap heat) of greenhouse gases.

See note.

The HFC impact still stands just below 0.8% of the total. It is anticipated that this share will hardly be higher in the future if the proposals for an international HFC phase-down will be adopted.

By contrast, the contribution of the five more important greenhouse gases account for 96 % of the total impact : CO2 65%, N2O 6%, CH4 17%, CFC 11 and 12 8 %. Other ozone depleting substances (ODS) account for most of the 3.2% remaining, after the contribution from HFCs.

The 15 minor halogenated gases, besides HFCs 134a, 152a, 23, 143a, and 125, are CFC-113, CCl4, CH3CCl3, HCFCs 22, 141b and 142b, SF6, and Halons 1211, 1301 and 2402.

The radiative forcing (ability of all greenhouse gases to trap heat) increased 34% from 1990 to 2013 (by ~0.74 watts m-2), CO2 has accounted for nearly 80% of this increase (~0.59 watts m-2). It is the CFC PHASE OUT, and the substitution of CFCs and HCFCs, notably by HFCs, that avoided the global radiative forcing to be even as much as 0.3 W/m2 higher, corresponding to more than half of the increase in radiative forcing due to CO2 alone since 1990.

The Figure shows the share of the long-lived, well-mixed greenhouse gases. The impacts from PFCs and SF6 are too low to appear on this scale of graph.

Source : AGGI and Private Communication (for the 15 minor gases)  

Note : The results reported here are based mainly on atmospheric measurements of long-lived, well mixed gases and have small uncertainties. They encompass all emissions of greenhouse gases, including those from countries that do not report under the Rio Convention.